/*******************************************************************************
 * Copyright 2006, 2017 Jerry Huxtable, Martin Davis
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * This file was semi-automatically converted from the public-domain USGS PROJ source.
 */
package org.locationtech.proj4j.proj;

import org.locationtech.proj4j.ProjCoordinate;
import org.locationtech.proj4j.ProjectionException;
import org.locationtech.proj4j.util.ProjectionMath;

public class CollignonProjection extends Projection {

	private final static double FXC = 1.12837916709551257390;
	private final static double FYC = 1.77245385090551602729;
	private final static double ONEEPS = 1.0000001;

	public ProjCoordinate project(double lplam, double lpphi, ProjCoordinate out) {
		if ((out.y = 1. - Math.sin(lpphi)) <= 0.)
			out.y = 0.;
		else
			out.y = Math.sqrt(out.y);
		out.x = FXC * lplam * out.y;
		out.y = FYC * (1. - out.y);
		return out;
	}

	public ProjCoordinate projectInverse(double xyx, double xyy, ProjCoordinate out) {
		double lpphi = xyy / FYC - 1.;
		if (Math.abs(out.y = 1. - lpphi * lpphi) < 1.)
			out.y = Math.asin(lpphi);
		else if (Math.abs(lpphi) > ONEEPS) throw new ProjectionException("I");
		else	out.y = lpphi < 0. ? -ProjectionMath.HALFPI : ProjectionMath.HALFPI;
		if ((out.x = 1. - Math.sin(lpphi)) <= 0.)
			out.x = 0.;
		else
			out.x = xyx / (FXC * Math.sqrt(out.x));
		out.y = lpphi;
		return out;
	}

	/**
	 * Returns true if this projection is equal area
	 */
	public boolean isEqualArea() {
		return true;
	}

	public boolean hasInverse() {
		return true;
	}

	public String toString() {
		return "Collignon";
	}

}
